Apparatus adapted for membrane-mediated electropolishing

1. An apparatus for use in membrane-mediated electropolishing of a work-piece having a surface comprising metal, said apparatus comprising: (a) a source of low-conductivity fluid adapted to supply low-conductivity fluid to at least a portion of the surface of the work-piece, wherein the conductivity of the low-conductivity fluid is less than about 2000 μS/cm; (b) a cathode half-cell comprising: (i) a fully or partially enclosed volume, cavity or vessel; (ii) a conductive electrolyte solution or gel which partially or essentially fills the fully or partially enclosed volume, cavity or vessel, wherein the conductive electrolyte solution or gel comprises positively and negatively charged ions, and has a conductivity greater than about 10 mS/cm; (iii) a cathode in contact with the electrolyte solution or gel; and (iv) an ion-conducting membrane which forms a surface of the fully or partially enclosed volume, cavity or vessel, wherein at least a portion of the internal surface of said membrane contacts the electrolyte solution or gel and the external surface of that portion of the membrane is accessible to contact a metal work piece, and wherein at least a portion of the conductive electrolyte solution or gel is interposed between the cathode and the internal surface of the ion-conducting membrane; (v) an inlet and an exit adapted to allow conductive electrolyte solution or gel to be circulated through the volume, wherein the inlet and exit are fluidly connected to a pump adapted to circulate the conductive electrolyte solution or gel between the partially or fully enclosed volume and the pump; (c) a DC electrical power source having a positive voltage terminal adapted to be electrically connected to the surface of the work-piece and having a negative voltage terminal electrically connected to the cathode; (d) a structure for movably contacting a portion of the external surface of the membrane to the work-piece; and (e) at least one of a filter, a de-gasser, a heat exchanger, and an apparatus to adjust the composition of the conductive electrolyte solution or gel, fluidly connected to the pump.

2. An apparatus for use in membrane-mediated electropolishing of a work-piece having a surface comprising metal, said apparatus comprising: (a) a source of low-conductivity fluid adapted to supply low-conductivity fluid to at least a portion of the surface of the work-piece, wherein the conductivity of the low-conductivity fluid is less than about 2000 μS/cm; (b) a cathode half-cell comprising: (i) a fully or partially enclosed volume, cavity or vessel; (ii) a conductive electrolyte solution or gel which partially or essentially fills the fully or partially enclosed volume, cavity or vessel, wherein the conductive electrolyte solution or gel comprises positively and negatively charged ions, and has a conductivity greater than about 10 mS/cm; (iii) a cathode in contact with the electrolyte solution or gel; and (iv) an ion-conducting membrane which forms a surface of the fully or partially enclosed volume, cavity or vessel, wherein at least a portion of the internal surface of said membrane contacts the electrolyte solution or gel and the external surface of that portion of the membrane is accessible to contact a metal work piece, and wherein at least a portion of the conductive electrolyte solution or gel is interposed between the cathode and the internal surface of the ion-conducting membrane; (c) a DC electrical power source having a positive voltage terminal adapted to be electrically connected to the surface of the work-piece and having a negative voltage terminal electrically connected to the cathode; (d) a structure for movably contacting a portion of the external surface of the membrane to the work-piece; and (e) a structure which exerts a force on the membrane, wherein the force substantially divides a single contactable surface area of the membrane if the structure was absent into a plurality of smaller contactable surface areas, and (i) the structure is joined to the exterior surface of the membrane; or (ii) the structure is movable relative to the exterior surface of the membrane; or (iii) the structure comprises channels adapted to distribute a low-conductivity fluid to the surface of the work-piece.

3. An apparatus for use in membrane-mediated electropolishing of a work-piece having a surface comprising metal, said apparatus comprising: (a) a source of low-conductivity fluid adapted to supply low-conductivity fluid to at least a portion of the surface of the work-piece, wherein the conductivity of the low-conductivity fluid is less than about 2000 μS/cm; (b) a cathode half-cell comprising: (i) a fully or partially enclosed volume, cavity or vessel; (ii) a conductive electrolyte solution or gel which partially or essentially fills the fully or partially enclosed volume, cavity or vessel, wherein the conductive electrolyte solution or gel comprises positively and negatively charged ions, and has a conductivity greater than about 10 mS/cm; (iii) a cathode in contact with the electrolyte solution or gel; and (iv) an ion-conducting membrane which forms a surface of the fully or partially enclosed volume, cavity or vessel, wherein at least a portion of the internal surface of said membrane contacts the electrolyte solution or gel and the external surface of that portion of the membrane is accessible to contact a metal work piece, and wherein at least a portion of the conductive electrolyte solution or gel is interposed between the cathode and the internal surface of the ion-conducting membrane; (c) a DC electrical power source having a positive voltage terminal adapted to be electrically connected to the surface of the work-piece and having a negative voltage terminal electrically connected to the cathode; (d) a structure for movably contacting a portion of the external surface of the membrane to the work-piece; and (e) a porous permeable compliant pad disposed between the cathode and the membrane or a porous backing, adapted to stiffen the membrane, disposed between the cathode and the membrane.

4. An apparatus for use in membrane-mediated electropolishing of a work-piece having a surface comprising metal, said apparatus comprising: (a) a source of low-conductivity fluid adapted to supply low-conductivity fluid to at least a portion of the surface of the work-piece, wherein the conductivity of the low-conductivity fluid is less than about 2000 μS/cm; (b) a cathode half-cell comprising: (i) a fully or partially enclosed volume, cavity or vessel; (ii) a conductive electrolyte solution or gel which partially or essentially fills the fully or partially enclosed volume, cavity or vessel, wherein the conductive electrolyte solution or gel comprises positively and negatively charged ions, and has a conductivity greater than about 10 mS/cm; (iii) a cathode in contact with the electrolyte solution or gel; and (iv) an ion-conducting membrane which forms a surface of the fully or partially enclosed volume, cavity or vessel, wherein at least a portion of the internal surface of said membrane contacts the electrolyte solution or gel and the external surface of that portion of the membrane is accessible to contact a metal work piece, and wherein at least a portion of the conductive electrolyte solution or gel is interposed between the cathode and the internal surface of the ion-conducting membrane; (c) a DC electrical power source having a positive voltage terminal adapted to be electrically connected to the surface of the work-piece and having a negative voltage terminal electrically connected to the cathode; and (d) a structure for movably contacting a portion of the external surface of the membrane to the work-piece; wherein the membrane comprises a strip of membrane material that can be moved relative to the fully enclosed volume, so that on moving the strip a different area of the strip becomes the external surface accessible to contact the surface of the work-piece.

5. A cathode half-cell apparatus adapted for use in membrane-mediated electropolishing of a work-piece having a surface comprising metal, said cathode half-cell apparatus comprising: (a) a fully or partially enclosed volume; (b) a conductive electrolyte solution or gel having a conductivity greater than about 5 mS/cm disposed within the fully or partially enclosed volume; (c) a cathode at least partially disposed within the fully or partially enclosed volume; and (d) a charge-selective ion-conducting membrane which forms a surface of the fully or partially enclosed volume, wherein said membrane comprises an internal surface and an external surface, wherein the internal surface of said membrane contacts the electrolyte solution or gel and the external surface is accessible to contact the surface of the work-piece, and wherein the electrolyte solution or gel additionally contacts the cathode and wherein at least a portion of the conductive electrolyte solution or gel is interposed between the cathode and the internal surface of the charge-selective ion-conducting membrane, wherein the external surface of the membrane accessible to contact the surface of the work-piece is substantially curved to allow only a portion of the external surface to contact a flat work-piece surface at any one time, and the external surface accessible to contact the surface of the work-piece forms a cylindrical shape.

6. An apparatus for use in membrane-mediated electropolishing of a work-piece having a surface comprising metal, said apparatus comprising: (a) a source of low-conductivity fluid adapted to supply low-conductivity fluid to at least a portion of the surface of the work-piece, wherein the conductivity of the low-conductivity fluid is less than about 2000 μS/cm; (b) at least two cathode half-cells, each comprising: (i) a fully or partially enclosed volume, cavity or vessel; (ii) a conductive electrolyte solution or gel which partially or essentially fills the fully or partially enclosed volume, cavity or vessel, wherein the conductive electrolyte solution or gel comprises positively and negatively charged ions, and has a conductivity greater than about 10 mS/cm; (iii) a cathode in contact with the electrolyte solution or gel; and (iv) an ion-conducting membrane which forms a surface of the fully or partially enclosed volume, cavity or vessel, wherein at least a portion of the internal surface of said membrane contacts the electrolyte solution or gel and the external surface of that portion of the membrane is accessible to contact a metal work piece, and wherein at least a portion of the conductive electrolyte solution or gel is interposed between the cathode and the internal surface of the ion-conducting membrane; (c) a DC electrical power source having a positive voltage terminal adapted to be electrically connected to the surface of the work-piece and having a negative voltage terminal electrically connected to the cathode; and (d) a structure for movably contacting a portion of the external surface of the membrane to the work-piece, comprising: (i) a plurality of individual rods, and wherein different half-cells are adapted to move laterally along different rods during electropolishing of a work-piece; or (ii) at least two concentric rings each having at least one half-cell mounted thereon, and wherein the concentric rings are adapted to rotate about a center of rotation each at a pre-selected rotational velocity.

7. An apparatus for use in membrane-mediated electropolishing of a work-piece having a surface comprising metal, said apparatus comprising: (a) a source of low-conductivity fluid adapted to supply low-conductivity fluid to at least a portion of the surface of the work-piece, wherein the conductivity of the low-conductivity fluid is less than about 2000 μS/cm; (b) a cathode half-cell comprising: (i) a fully or partially enclosed volume, cavity or vessel; (ii) a conductive electrolyte solution or gel which partially or essentially fills the fully or partially enclosed volume, cavity or vessel, wherein the conductive electrolyte solution or gel comprises positively and negatively charged ions, and has a conductivity greater than about 10 mS/cm; (iii) a cathode in contact with the electrolyte solution or gel; and (iv) an ion-conducting membrane which forms a surface of the fully or partially enclosed volume, cavity or vessel, wherein at least a portion of the internal surface of said membrane contacts the electrolyte solution or gel and the external surface of that portion of the membrane is accessible to contact a metal work piece, and wherein at least a portion of the conductive electrolyte solution or gel is interposed between the cathode and the internal surface of the ion-conducting membrane; (c) a DC electrical power source having a positive voltage terminal adapted to be electrically connected to the surface of the work-piece and having a negative voltage terminal electrically connected to the cathode; and (d) a structure for movably contacting a portion of the external surface of the membrane to the work-piece; wherein the fully enclosed volume is subject to a positive hydrostatic pressure greater than the ambient atmospheric pressure, and the apparatus further comprises a vessel adapted to hold a volume of low-conductivity fluid, wherein the membrane and the surface of the work-piece are disposed within the volume of low-conductivity fluid at a point a predetermined distance beneath the surface of the volume of low-conductivity fluid.